The objective of this research is to determine: 1. Is the distribution of the birth dates of the population of schizophrenic patients similar to the non-schizophrenic population? 2. Is there a seasonal phenomenon in the birth dates of the schizophrenic patients associated with: a. sex of the patient; b. age at first diagnosis; c. clinical subtype diagnosis; d. s.e.s. at first diagnosis? METHODS: Design: Case-control: Cases: All residents of Monroe County, N.Y., who were first diagnosed schizophrenic during the period 1-69 - 12-71; Controls: All residents of Monroe County, N.Y. (1970 Census).